PFD is short for prepared for dyeing.
The short explanation is that PFD fabrics are treated so that they will take dyes really well.
Generally PFD fabrics have no optic whiteners or any sizing, starches, or finishes that could interfere with the dye.
This means that you can dye the fabric right off the bolt without having to wash first.
Some people still like to wash before dyeing. I prewashed when I first started dyeing, but after experimenting with an unwashed piece and seeing no difference in color between a dyed prewashed and unwashed piece, I no longer wash my fabric before dyeing.
Do you have to use PFD fabric for dyeing?
You can use just regular cotton for dyeing but you definitely have to wash it at first.
However, not all fabric is going to take dye well. You’ll probably want to dye a smaller test piece before going crazy and dyeing a whole bunch of the fabric. I’ve dyed some pieces of regular cotton that took the dye just as well as my PFD fabric, but I’ve also had some that didn’t take the dye well, making the resulting color much lighter.
Seeing as there isn’t really a price difference between regular cotton and PFD, I prefer just to get the stuff that I know is going to work without the extra work of washing beforehand. Less work is always a plus in my book!